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United States Patent |
5,609,690
|
Watanabe
,   et al.
|
March 11, 1997
|
Vacuum plasma processing apparatus and method
Abstract
A vacuum plasma processing apparatus includes a vacuum processing container
accommodating a to-be-processed substrate, a feeding device for feeding a
reaction gas to the container, a vacuumizing device for discharging a gas
in the container therefrom, a susceptor for holding the to-be-processed
substrate arranged in the container, split electrodes arranged in a
deltaic lattice at a wall surface of the container facing the
to-be-processed substrate, and a power source unit for impressing to the
slit electrodes three-phase RF powers having three phases different from
each other. When the electrodes are arranged in an orthogonal lattice at
the wall surface of the continuer, the power source unit impresses thereto
two-phase RF powers having two phases different from each other.
Inventors:
|
Watanabe; Syouzou (Moriguchi, JP);
Suzuki; Masaki (Hirakata, JP);
Nakayama; Ichiro (Kadoma, JP);
Okumura; Tomohiro (Neyagawa, JP)
|
Assignee:
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Matsushita Electric Industrial Co., Ltd. (Osaka-fu, JP)
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Appl. No.:
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389229 |
Filed:
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February 15, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
118/723E; 118/723ER |
Intern'l Class: |
C23C 016/00 |
Field of Search: |
118/723 E,723 ER
156/345
204/298.08,298.39
313/231.31
315/111.21
|
References Cited
U.S. Patent Documents
5330606 | Jul., 1994 | Kubota et al. | 156/345.
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5424905 | Jun., 1995 | Nomura et al. | 361/235.
|
Foreign Patent Documents |
58-42226 | Nov., 1983 | JP.
| |
60-153129 | Dec., 1985 | JP.
| |
62-273731 | Nov., 1987 | JP.
| |
3-30424 | Aug., 1991 | JP.
| |
60-61185 | Apr., 1994 | JP.
| |
Primary Examiner: Breneman; R. Bruce
Assistant Examiner: Chang; Joni Y.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
What is claimed is:
1. A vacuum plasma processing apparatus comprising:
a vacuum processing container accommodating a to-be-processed substrate;
a feeding means for feeding a reaction gas to the container;
a vacuumizing means for discharging a gas in the container therefrom;
a susceptor for holding the to-be-processed substrate arranged in the
container;
split electrodes arranged in a lattice at a wall surface of the container
facing the to-be-processed substrate; and
a power source unit for impressing to the split electrodes RF powers having
phases different from each other,
wherein the split electrodes are arranged in such a lattice at the wall
surface of the container facing the to-be-processed substrate that phases
and phase voltages of the RF powers form a Lissajous figure.
2. The vacuum plasma processing apparatus as claimed in claim 1, wherein
the lattice is a deltaic lattice.
3. The vacuum plasma processing apparatus as claimed in claim 1, wherein
the lattice is an orthogonal lattice.
4. The vacuum plasma processing apparatus as claimed in claim 2, wherein an
RF power is added to the susceptor.
5. The vacuum plasma processing apparatus as claimed in claim 2, wherein
the RF powers impressed to the split electrodes by the power source unit
are three-phase RF powers of about 120.degree. phase difference.
6. The vacuum plasma processing apparatus as claimed in claim 2, wherein
each of the split electrodes has projecting semi-spherical surface facing
the to-be-processed substrate.
7. The vacuum plasma processing apparatus as claimed in claim 2, wherein
each of the split electrodes is formed in a circular cylinder.
8. The vacuum plasma processing apparatus as claimed in claim 2, wherein
each of the split electrodes is formed in a quadrangular prism with curved
corners.
9. The vacuum plasma processing apparatus as claimed in claim 2, wherein
each of the split electrodes is formed in a hexagonal prism with curved
corners.
10. The vacuum plasma processing apparatus as claimed in claim 2, wherein
the container is made of insulating material.
11. The vacuum plasma processing apparatus as claimed in claim 2, wherein
the container is made of conductive material and an insulating material is
disposed between each of the electrode and the container.
12. The vacuum plasma processing apparatus as claimed in claim 3, wherein
an RF power is added to the susceptor.
13. The vacuum plasma processing apparatus as claimed in claim 3, wherein
the RF powers impressed to the slit electrodes by the power source unit
are two-phase RF powers of about 180.degree. phase difference.
14. The vacuum plasma processing apparatus as claimed in claim 3, wherein
each of the split electrodes has projecting semi-spherical surface facing
the to-be-processed substrate.
15. The vacuum plasma processing apparatus as claimed in claim 3, wherein
each of the split electrodes is formed in a circular cylinder.
16. The vacuum plasma processing apparatus as claimed in claim 3, wherein
each of the electrodes is formed in a quadrangular prism with curved
corners.
17. The vacuum plasma processing apparatus as claimed in claim 3, wherein
each of the electrodes is formed in a hexagonal prism with curved corners.
18. The vacuum plasma processing apparatus as claimed in claim 3, wherein
the container is made of insulating material.
19. The vacuum plasma processing apparatus as claimed in claim 3, wherein
the container is made of conductive material and an insulating material is
disposed between each of the electrode and the container.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum plasma processing apparatus and
method used in processing a semiconductor wafer or a liquid crystal
display substrate, etc. by way of dry etching, CVD, sputtering, or other
kinds of surface treatment.
A conventional vacuum plasma processing apparatus will be described by way
of example.
The constitution of the apparatus is shown in FIGS. 21 and 22. In FIG. 21,
a susceptor 3 for holding a to-be-processed board 2 is disposed in a
vacuum processing container 1 which has a reaction gas feed port 7 and a
vacuum pump 8. An RF generator 4 is connected to the susceptor 3. A
cylindrical electrode 5 arranged above the susceptor 3 is connected to an
RF generator 6. Specifically, the cylindrical electrode 5 is divided or
split to three parts, and three parts are connected to the corresponding
RF generators 6 of every 120.degree. or so different phases.
The operation of the apparatus will now be described.
While the gas in the container is discharged from the container 1 by the
vacuum pump 8, a reaction gas is introduced into the container 1 from the
feed port 7 to bring about plasma. The reaction gas in the container is
kept at a suitable pressure. RF powers of phases approximately 120.degree.
different each other are applied from the RF generators 6 to the split
three parts of the electrode 5, whereby an electric field is formed in the
container 1. As a result, plasma is generated because of the acceleration
of electrons by the electric field. The to-be-processed board 2 is
accordingly surface-treated in the vacuum plasma processing apparatus.
At the same time, the energy of ions entering the to-be-processed board 2
is controllable in the apparatus as the RF generator 4 impresses an RF
power to the susceptor 3.
In the conventional structure as above, the intensity of the plasma is
large in the vicinity of the electrode 5, whereas the intensity becomes
small as it is closer to the center of the container 1. Therefore, the
etching speed and the forming speed of a film on the substrate 2 become
irregular, turning the apparatus unfit to process particularly a substrate
of a large area.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a vacuum plasma
processing apparatus and method which can generate uniform plasma on a
to-be-processed substrate.
In accomplishing these and other objects, according to one aspect of the
present invention, there is provided a vacuum plasma processing apparatus
comprising: a vacuum processing container accommodating a to-be-processed
substrate; a feeding means for feeding a reaction gas to the container; a
vacuumizing means for discharging a gas in the container therefrom; a
susceptor for holding the to-be-processed substrate arranged in the
container; split electrodes arranged in a lattice at a wall surface of the
container facing the to-be-processed substrate; and a power source unit
for impressing to the slit electrodes RF powers having phases different
from each other, wherein the electrodes are arranged in such a lattice at
the wall surface of the container facing the to-be-processed substrate
that phases and phase voltages of the RF powers form a Lissajous figure.
According to another aspect of the present invention, there is provided a
vacuum plasma processing method comprising steps of: feeding a reaction
gas to a vacuum processing container accommodating a to-be-processed
substrate which is held on a susceptor and discharging a gas in the
container therefrom; and impressing RF powers having phases different from
each other split electrodes in such a lattice at the wall surface of the
container facing the to-be-processed substrate that phases and phase
voltages of the RF powers form a Lissajous figure.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will become
clear from the following description taken in conjunction with the
preferred embodiments thereof with reference to the accompanying drawings,
in which:
FIG. 1 is a structural diagram of a vacuum plasma processing apparatus
according to a first embodiment of the present invention;
FIG. 2 is an arrangement diagram of split electrodes in the vacuum plasma
processing apparatus of FIG. 1;
FIG. 3 is a diagram showing the phase difference of RF powers impressed to
the split electrodes of the vacuum plasma processing apparatus of FIG. 1;
FIG. 4 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
0.degree.;
FIG. 5 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
60.degree.;
FIG. 6 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
120.degree.;
FIG. 7 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
180.degree.;
FIG. 8 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
240.degree.;
FIG. 9 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
360.degree.;
FIG. 10 is a structural diagram of a vacuum plasma processing apparatus
according to a second embodiment of the present invention;
FIG. 11 is an arrangement diagram of split electrodes in the vacuum plasma
processing apparatus of FIG. 10;
FIG. 12 is a diagram showing the phase difference of RF powers impressed to
the split electrodes of the vacuum plasma processing apparatus of FIG. 10;
FIG. 13 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 10 is
90.degree.;
FIG. 14 is an instantaneous distribution diagram of principal lines of
electric forces when the phase .theta. of the RF power impressed to the
split electrodes of the vacuum plasma processing apparatus of FIG. 1 is
270.degree.;
FIGS. 15A and 15B are a sectional side view and a plan view of the split
electrode which is a circular cylinder with the electrode arranged at the
container;
FIGS. 16A and 16B are a sectional side view and a plan view of the split
electrode which is a circular cone with the electrode arranged at the
container;
FIGS. 17A and 17B are a sectional side view and a plan view of the split
electrode which is a quadrangular prism having curved corners with the
electrode arranged at the container;
FIGS. 18A and 18B are a sectional side view and a plan view of the split
electrode which is a hexagonal prism having curved corners with the
electrode arranged at the container;
FIG. 19 is a structural diagram of a vacuum plasma processing apparatus
wherein the wall surface of an insulating body of a vacuum processing
container accommodating split electrodes is semi-spherical as another
embodiment of the present invention;
FIG. 20 is a structural diagram when an insulating part is arranged between
the wall surface of a vacuum processing container accommodating the split
electrodes and the split electrode while the wall surface is a conductive
body as a further embodiment of the present invention;
FIG. 21 is a structural diagram of a conventional vacuum plasma processing
apparatus;
FIG. 22 is an arrangement diagram of split electrodes in the apparatus of
FIG. 21;
FIG. 23 is a graph showing the relationship between the positions of 6-inch
and 8-inch substrates and the plasma density thereon in a case where the
apparatus according to the first embodiment of the present invention is
used; and
FIG. 24 is a graph showing the relationship between the positions of 6-inch
and 8-inch substrates and the plasma density thereon in a case where the
apparatus according to the conventional example shown in FIG. 21 is used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the description of the present invention proceeds, it is to be noted
that like parts are designated by like reference numerals throughout the
accompanying drawings.
The present invention will be described in conjunction with preferred
embodiments thereof with reference to the accompanying drawings.
FIGS. 1 and 2 are structural diagrams of a vacuum plasma processing
apparatus according to a first embodiment of the present invention. In
FIG. 1, a susceptor 13 holding a to-be-processed substrate 12 is set in a
vacuum processing container 11 having a reaction gas feed port 7 and a
vacuum pump 18. The susceptor 13 is connected to an RF generator 14
provided for controlling the energy of ions. As is shown in FIG. 2,
projecting semi-spherical electrodes (split electrodes) 15a, 15b, 15c are
arranged to assume a deltaic lattice at the wall surface of an insulator
of the vacuum processing container 11 facing the susceptor 13. RF
generators 16a, 16b, 16c are respectively connected to the split
electrodes 15a, 15b, 15c to generate plasma.
The above apparatus operates in a manner as will be described below.
A reaction gas to generate plasma is fed from a reaction gas feed port 17
into the vacuum processing container 11. During this time, the gas in the
container 11 is discharged by the vacuum pump 18. The reaction gas is kept
in the container 11 at a suitable pressure. Subsequently, RF powers of
phases different approximately 120.degree. each other as shown in FIG. 3
are impressed from the RF generators 16a, 16b, 16c to the electrodes 15a,
15b, 15c, respectively. In consequence, an electric field is generated in
the vacuum processing container 11. Since the electrons are accelerated by
the electric field, plasma is produced. The lines of electric forces
quickly change at this time because of the phase difference of the RF
powers. The change of the principal lines of electric forces is
represented in FIGS. 4 through 9. In FIGS. 1, 4 through 9, reference
characters (a), (b), and (c) denote the electrode 15a, 15b, and 15c,
respectively. FIG. 4 indicates the state of the principal lines of
electric forces when the phase .theta. is 0.degree. in FIG. 3. Similarly,
FIGS. 5, 6, 7, 8, and 9 respectively show the states when the phase
.theta. is 60.degree., 120.degree., 180.degree., 240.degree., and
360.degree.. Owing to the quick change of the lines of electric forces as
depicted hereinabove, it becomes possible to generate uniform plasma 19
along the wall surface in the container 11 where the electrodes 15a, 15b,
15c are arranged in the deltaic lattice.
Moreover, if an RF power is optionally applied to the susceptor 13 by the
RF generator 14, the density of the plasma 19 and the energy of ions
entering the substrate 12 are controllable separately from each other,
thereby achieving vacuum plasma processing in the optimum state.
The constitution of a vacuum plasma processing apparatus according to a
second embodiment of the present invention is shown in FIGS. 10 and 11. In
FIG. 10, a vacuum processing container 21 has a reaction gas feed port 27
and a vacuum pump 28. A susceptor 23 loading a to-be-processed substrate
22 thereon is set in the container 21. The susceptor 23 is connected to an
RF generator 24 for controlling the energy of ions. At the wall surface of
an insulator of the container 21 confronting to the susceptor 23 are
latticed projecting semi-spherical electrodes (split electrodes) 25a, 25b
orthogonal to each other as is clearly shown in FIG. 11. RF generators
26a, 26b are connected to the split electrodes 25a, 25b to generate
plasma.
The operation of the above vacuum plasma processing apparatus will be
described now.
While the gas is discharged from the vacuum processing container 21 by the
vacuum pump 28, a reaction gas to generate plasma is fed through the feed
port 27 into the container 21. The reaction gas is maintained in the
container 21 at a suitable pressure. RF powers of phases of about
180.degree. difference as shown in FIG. 12 are impressed to the orthogonal
electrodes 25a, 25b from the RF generators 26a, 26b, whereby an electric
field is generated in the container 21. The electric field accelerates
electrons, leading to the generation of plasma. At this time, the lines of
electric forces quickly change due to the phase difference of the RF
powers. The change of the principal lines of electric forces is indicated
in FIGS. 13 and 14 respectively representing the state where the phase
.theta. is 90.degree. in FIG. 12 and 270.degree. in FIG. 14. In FIGS. 10,
11, 13, and 14, reference characters (a) and (b) denote the electrode 25a
and 25b, respectively. The above rapid change of the lines of electric
forces contributes to form uniform plasma 29 along the wall surface in the
container 21 where the electrodes 25a, 25b are disposed.
Moreover, when an RF power is impressed to the susceptor 23 from the RF
generator 24, the density of the plasma 29 and the energy of ions entering
the substrate 22 can be controlled individually. Accordingly, optimum
vacuum plasma processing is realized.
Although the split electrodes are projecting or convex semi-spherical in
the first and second embodiments as above, the electrodes may be formed in
different kinds of shapes, for example, a circular cylinder of FIGS. 15A
and 15B, a circular cone of FIGS. 16A and 16B, a quadrangular prism having
curved corners as in FIGS. 17A and 17B, or a hexagonal prism with curved
corners as illustrated in FIGS. 18A and 18B. Reference numeral 50 denotes
a packing between the electrode and the container 11 in FIGS. 15A, 16A,
17A, and 18A. The reason that each electrode has the projecting
semi-spherical surface is to increase the exposed area of each electrode
which is exposed to the plasma. The reason why each corner of the
electrode should be curved is to prevent any abnormal electric discharge
at a non-curved corner of each electrode.
The wall surface of the insulator of the vacuum processing container is a
flat surface in the first and second embodiments. However, a
semi-spherical surface as shown in FIG. 19 may be employable the present
invention.
Additionally, although the wall surface of the vacuum processing container
is the insulator in the first and second embodiments, the present
invention is applicable to a mechanism in FIG. 20 wherein a wall surface
31 of the vacuum processing container accommodating split electrodes 32 is
rendered a conductive body, while an insulating component 33 is disposed
between each electrode 32 and the wall surface 31.
Although in the embodiments the electrodes are arranged in the deltaic
lattice or orthogonal lattice, the electrodes may be arranged in such a
lattice at the wall surface of the container facing the to-be-processed
substrate that the phases and phase voltages of the RF powers form a
Lissajous figure such as figures shown in FIGS. 3 and 12. In the deltaic
lattice, the shape of each deltaic shape is not limited to a regular
triangle which is shown in FIG. 2 and formed by the electrodes 15a, 15b,
and 15c and may be formed in an isosceles triangle, for example. Moreover,
the shape of each electrode may be formed in such a shape that the phases
and phase voltages of the RF powers form a Lissajous figure such as
figures shown in FIGS. 3 and 12.
Furthermore, as an example, each electrode 15, 25, 32 is made of aluminum,
the insulator of the container 11, 21 is made of ceramic, the wall surface
31 is made of stainless steel, and the insulating component 33 is made of
ceramic, preferably.
FIG. 23 shows the relationship between the positions of 6-inch and 8-inch
substrates and the plasma density thereon in a case where the apparatus
according to the first embodiment of the present invention is used while
at the inner pressure of the container of 5 mTorr and Ar of 30SCCM, RF
powers of 100 W are impressed to the electrodes 15a, 15b, 15c. The
occupied position of each substrate is indicated by 6" and 8" in FIG. 23
and the reference center of each substrate is a position of 22 cm in FIG.
23. When the diameter of each electrode is 6 inch, the density of the
plasma is 1.0.times.10.sup.11 cm.sup.-3 and the uniformity thereof is
.+-.4.8%. When the diameter of each electrode is 8 inch, the density of
the plasma is 1.0.times.10.sup.11 cm.sup.-3 and the uniformity thereof is
.+-.10%.
FIG. 24 shows the relationship between the positions of 6-inch and 8-inch
substrates and the plasma density thereon in a case where the apparatus
according to the conventional example shown in FIG. 21 is used while under
the inner pressure of the container of 5 mTorr and Ar of 30SCCM, RF powers
of 100 W are impressed to the three electrodes 5. The occupied position of
each substrate is indicated by 6' and 8' in FIG. 24 and the reference
center of each substrate is a position of 22 cm in FIG. 23. When the
diameter of each electrode is 6 inch, the density of the plasma is
4.5.times.10.sup.10 cm.sup.-3 and the uniformity thereof is .+-.6.5% which
is worse than the example of the first embodiment. When the diameter of
each electrode is 8 inch, the density of the plasma is 4.5.times.10.sup.10
cm.sup.-3 and the uniformity thereof is .+-.21% which is worse than the
example of the first embodiment.
In three tests as specific examples of the embodiment of FIG. 1, aluminum
alloy, silicon, and platinum are etched.
In a first test where aluminum alloy is etched, an etching gas mixing
BCl.sub.3, Cl.sub.2, and N.sub.2 with each other is introduced in the
container and inner pressure of the container is maintained at 2 Pa. An RF
power of 60 MHz is impressed to the electrodes 15a, 15b, and 15c in FIG. 2
at each 200 W while the phases are shifted about 120.degree.. An RF power
of 13.56 MHz is impressed to the susceptor 13 at 150 W. In the first test,
the number of the electrodes is 19 and electrodes which have a shortest
distance from the electrode 15a are electrodes 15b and 15c. As a result of
the first test, the speed of the aluminum alloy is 1 .mu.m/min and the
uniformity of an 8-inch substrate is .+-.5% which is good. In cases where
the numbers of the electrodes are changed to 7 and 14, the speed is not
changed in the both cases, but the uniformity of the latter case is better
than the former case.
In a second test where silicon is etched, an etching gas mixing HBr and
O.sub.2 with each other is introduced in the container and inner pressure
of the container is maintained at 1 Pa. The method for impressing an RF
power to the electrodes 15a, 15b, and 15c is the same as the first test.
An RF power of 13.56 MHz is impressed to the susceptor 13 at 200 W. As a
result of the second test, the speed of the silicon is 0.3 .mu.m/min and
the uniformity of an 8-inch substrate is .+-.4% which is good.
In a third test where platinum is etched, an etching gas of Cl.sub.2 is
introduced in the container and inner pressure of the container is
maintained at 1 Pa. The method for impressing an RF power to the
electrodes 15a, 15b, and 15c is the same as the first test. An RF power of
13.56 MHz is impressed to the susceptor 13 at 500 W. As a result of the
third test, the speed of the platinum is 0.2 .mu.m/min and the uniformity
of an 8-inch substrate is .+-.4% which is good. In cases where the numbers
of the electrodes are changed to 7 and 14, the deposition amount of
reaction product in the latter is less than the former.
As is fully described hereinabove, according to the present invention, when
RF powers of different phases are impressed to the split electrodes in the
latticed arrangement on the wall surface in a vacuum processing container
facing a susceptor holding the to-be-processed substrate thereon, an
electric field is brought about between the split electrodes. Since the
electric field quickly changes between the split electrodes, uniform
high-density plasma is generated on the to-be-processed substrate.
Moreover, when an RF power is applied to a lower electrode loading the
to-be-processed substrate, the energy of ions reaching the substrate is
independently controllable.
Although the present invention has been fully described in connection with
the preferred embodiments thereof with reference to the accompanying
drawings, it is to be noted that various changes and modifications are
apparent to those skilled in the art. Such changes and modifications are
to be understood as included within the scope of the present invention as
defined by the appended claims unless they depart therefrom.
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